Heat stabilized polymeric 2, 3-dichloro-1,3-butadiene and process for obtaining same



Patented Aug. 1, 1950 UNITED STATES PATENT; OFFICE HEAT STABILIZEDPOLYMERIC 2,3-DI- CHLORO-L3-BUTADIENE AND PROCESS FOR OBTAINING SAMEArthur L. Barney, Wilmington, Del., assignorto E. I. du lont de Nemours& Company,:Wil-

mington, DeL, a corporation of Delaware No Drawing. Application March21; 1948, Serial No. 18,290 r 5 Claims. (Cl. 260-459) This inventionrelates to polymers of 2,3-diwas poured on a casting plate at 85 C. andthe chloro-l,3-butadiene having improved heat staplate temperaturegradually raised to 130 C. bility and to a method of obtaining theseheatuntil the solvent was evaporated. The film was stable polymers. thencooled quickly to room temperature, re-

The polymers of 2,3-dichloro-1,3-butadiene are 5 moved from the plateand placed in an oven at described in U. S. Patent 1,965,369. They areof 150 C. in which air was circulating, together with considerablepractical interest, for example as a similar but untreated film ofpoly-2,3-dichlorofreeze-reducing agents in polychloroprene. More1,3-butadiene for comparison. The films were recently it has been found(application S. N. examined at intervals for color and embrittle718,618, filed by A. L. Barney on December 26, ment, if any. i

1946) that films, filaments and the like of poly- The followingdithiocarbamates were used in merized 2,3-dichloro-1,3-butadiene can becold these tests: l 1 I drawn to permanently elongated structures ofgreat strength showing a characteristicorienta- LLO'deFamethyIeHB.dlmethyl tion diagram when examined by X-ray diffracl5(CHa)2NUS--(GH2)m-S*CN(CH@)z tion methods. However, the value of theseapplil i .g

cations of 2,3-dichloro-1,3-butadiene polymers is impaired by the factthat these polymers are suslfi-hexamethylene bls dlmethyl ceptible to ahigh degree of deterioration by heat; (GHSMNAJ;S (OH2)5 S C N(OH3)2Exposure of the polymers to a high temperature,

for example 150 0., for as little as two hours, 8 produces discolorationand embrittlement; the C, 1,3-trimethy1ene bis dimethy] samekind ofdeterioration occurs at lower temperatures, such as can be commonlyencountered (CHS)ZNT(I} ST(QH2)FST%(f N(CH?h in practice, on moreprolonged exposure. i

This invention has as an object a composition Mthylerle bisdimethyl ofmatter comprising heat stabilized polymer of 2,3-dichloro-1,3-butadiene.A further object is 3)2 |-SCHQ--S'fi- S)Q an effective and economicalmethod for prevents ing or for materially reducing the deterioration 3Oto which polymeric 2,3-dichloro-1,3-butadiene is h dlmethyl normallysubject. Other objects will appear here- (CH N. S (C]f ;s N(QH inaiter.l a :1

I have now found that polymers of 2,3-dichloro- 1,3-butadiene containingintimately mixed there- F. Methylene bis dlethyl with a minor amount byweight of an ester of an N,N-dialkyldithiocarbamic acid are effectivelyZommfifi-s onzs molnm stabilized against heat deterioration. Prefer- Iably, the stabilizer is an N,N-dialkyldith iocar- G. Ethyfidnelbisdummy] bamic ester of a primary alcohol having no sub- 40 1 a r r cstituent other than the alcoholic hydroxyl. The fi T --if-N(CH3)2 bestresults are obtained with his N',N-dia1kyldia r I s H3 s thiocarbamatesof dihydric primary alcohols having no substituent other than thealcoholic hy- Allyl dlmgthyl 3 droxyls. oH3)2N-o-soH2-oH=oHl Thedithiocarbamates for use in this invention 1 l v i l may be prepared bymethods described in the literature. The bis dithiocarbamates 0fdihydric f d ophenyl dim y alcohols may be preparedas described in U. S.Patent 2,384,577, caalsso. In the tests tabulated below, each stabilizers. I N02 was incorporated at 2% concentration into a 23- 2 butne 1,4bismmwutm dichloro-l,3-butadiene polymer by dissolving the polymer and2% by weight of the stabilizer in on-1g N-r -s oar on cn onrs-o can);xylene at about 100 C. The resultant Solution of the dithiocarbamate.

no substituents other than the alcoholic hydroxyls. The best results asregards heat stabilization are obtained with bisN,N-dialkyldithiocarbamates of dihydric primary alcohols having nosubstituent other than the alcoholic hydroxyls. The most usefulstabilizers are the N,Ndialkyldithiocarbamates, wherein the alkyl groupshave from 1 to 12 carbon atoms, of polymethylene glycols having from 6to 18 methylene groups between the alcoholic hydroxyls.

While as little as 0.1% of dithiocarbamate based on the weight of2,3-dichloro-1,3-butadiene polymer is sufficient to impartheat-stabilizing effects, it ispreferable to use at least 0.5% Althoughthe presence of the stabilizer in excess of that required is notparticularly important, it is unnecessary and uneconomical to use morethan 5% of the stabilizer, a generally useful proportion being between 1and 3%, based on the weight of the polymer.

The dithiocarbamate may be incorporated into the polymer by any suitablemethod, such as by solution in a mutual solvent followed by removal ofthe solvent, or by intimate mixing of the solids the following table. 2on. arubber mill, or by mixing aqueous disper- Aspect of film afterstorage at 150 C. for

Dithiocarbamate 4 hours 6 hours 8 hours 24 hours None (contro1) Yellow,brittle Brown, brittlc Dark brown" Too brittle to handle. A No change Nochange No change No color, good cold draw.

do dn Yellow, slightly brittle. V. 5]. yellow. Brown, slightly brittle.do D0. 51. yellow Do, Yellow Do. S1. yellow Do. Yellow D0, 81. yellowT)0. V. s1. dark Do. V. 51. yellow Sl. yellow Do. No change No change.V. s1. yellow, good cold draw.

dn rln D0; dn (in D0,

dn (ln Yellow, v. 51. brittle.

The film indicated at I in the table was slightly yellow at the start,because of the color of 2,4-

dinitrophenyl N,N.-dimethyldithiocarbamate.

It will be observed from the above table that all of the filmscontaining a, dithiocarbamate showed considerable improvement over thecontrol film from the standpoint of both embrittlement and developmentof color; The control was yellow even after only two hoursin the oven at150 C. and, after 24 hours, it had lost all utility as an industrialmaterial. The films containing a dithiocarbamate, on the other hand,showed a.

only slight embrittlement after 24 hours in this accelerated test and,in the most favorable cases, were as amenable to cold drawing after 24hours at 150 C. as they were. at thestart of the test. The stabilizedsamples were less discolored after 24 hours than the control after 4hours and, in the best cases, showed no yellowing or a very slight one.

In addition to the stabilizers mentioned above, others may be usedsuchas the N,l T-dipropyl, dihexyl, dioctyl, didodecyl etc.dithiocarbamicacid esters of. methanol, ethanol, butanol, hexyl alcohol, stearyl'alcohol, phenol, methoxyethanol, ethoxyethanol, tetramethylene glycol,octamethylene glycol, tetradecamethyl'ene glycol, octadecamethyleneglycol, dihydroxydiethyl ether, cyclohexanol, benzyl alcohol, etc.. Thepreferred materials because of their easier accessibility and freedomfrom side reactions are the N,N-dialkyldithiocarbamic esters of primaryalcohols having sions of they polymer andstabilizer. The dithiocarbamatemay also be introduced into the polymerization system (bulk, solution,emulsion, etc. after the 2,3-dichloro-l,3-butadiene polymerized to someextent.

Theinvention is particularly useful in the heatstabilization of2,3-dichloro-1,3-butadiene polymer in the form of shaped structures suchas films, filaments, moldings and the like, with or without addedmaterials such as plasticizers, pigments, antioxidants, reinforcingagents, etc.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

I claim:

1. A polymer of 2,3 dichloro 1,3-butadiene containing in minor amount,and in amount of at least 0.5% by weight thereof, anN,N-dialkyldithiocarbamate, in which the alkyl groups contain from 1 to12 carbon atoms, of a polymethylene glycol having from 6 to 18 methylenegroups between the alcoholic hydroxyls.

2. A polymer of 2,3-dichloro-1,3-butadiene containing in minor amount,and in amount of at least 0.1% by weight thereof, anN,N-dialkyldithiocarbamate, in which the alkyl groups contain from 1 to12 carbon atoms, of a dihydric primary alcohol in which the solesubstituent isthe alcoholic, hydroxyl,

5 3. A polymer of 2,3 dichloro 1,3- butadiene containing in minoramount, and in amount of at least 0.5% by weight thereof,1,10-decamethy1- ene bis dimethyldithiocarbamate.

4. A polymer of 2,3 dichloro 1,3 butadiene 5 containing in minor amount,and in amount 01' at least 0.5% by weight thereof, Lfi-hexamethylene bisdimethyldithiocarbamate.

5. A polymer of 2,3-dich1oro-1,3-butadiene containing in minor amount,andin amount of at least 0.5% by weight thereof, xylylene bisdin-butyldithiocarbamate.

ARTHUR L. BARN'EY.

6 REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,965,369 Carothers July 31, 19342,259,122 Walker Oct, 14, 1941 2,387,518 Lightbown Oct. 23, 1945 102,445,739 Rowland July 20, 1948 Certificate of Correction Patent No.2,516,945 August 1, 1950 ARTHUR L. BARNEY It is hereby certified thaterror appears in the printed specification of the above numbered patentrequiring correction as follows:

Column 2, line 53, for (C4Hg) read (0 119 and that the said LettersPatent should be read as corrected above, so that the same may conformto the record of the case in the Patent Office.

Signed and sealed this 14th day of November, A. D 1950.

THOMAS. F. MURPHY,

Assistant Commissioner of Patents.

1. A POLYMER OF 2,3 - DICHLORO - 1,3-BUTADIENE CONTAINING IN MINORAMOUNT, AND IN AMOUNT OF AT LEAST 0.5% BY WEIGHT THEREOF, ANN,N-DIALKYLDITHIOCARBAMATE, IN WHICH THE ALKYL GROUPS CONTAIN FROM 1 TO12 CARBON ATOMS, OF A POLYMETHYLENE GLYCOL HAVING FROM 6 TO 18 METHYLENEGROUPS BETWEEN THE ALCOHOLIC HYDROXYLS.